Migration question

What I was doing (and tell me if this is wrong, and the correct way to do it if possible) was putting a .forward file in the user directories that were moving.

So we'll use the example.com domain used in the webpage example.

mail comes to user@example.com. The MX points to mail.example.com. So the mail gets delivered to user on mail.example.com. In their home directory they have a .forward that sends the mail to user@zimbra.example.com.